Accident Overview
During the takeoff roll, the airplane experienced an abrupt swerve to the left. It then collided with a runway light and nosed over. The incident occurred approximately 350 feet from the point where the takeoff was initiated, indicating that the swerve began near the moment the tail wheel would have lifted off the runway.
Postaccident Examination
A detailed examination of the airplane after the accident revealed a malfunction in the tail steering arm mechanism. The tail steering arm was found to intermittently lock the rudder in a fully deflected position, with the trailing edge of the rudder displaced to the left. In this state, the tail wheel remained aligned with the airplane's centerline, masking the rudder deflection on the ground.
Damage Assessment
Physical evidence from the accident was consistent with a fully deflected rudder at the time the tail was lifted for takeoff. Specifically, the right tire exhibited scuffing on the circumference of its outboard sidewall, while the left tire showed no flat spots that would indicate a locked brake. This damage pattern aligns with the aerodynamic effect of a deflected rudder causing an abrupt yaw to the left once the tail wheel broke contact with the runway.
Mechanical Findings
The intermittent locking of the tail steering arm meant that the rudder could become stuck in a full-left deflection while the tail wheel remained straight. When the tail lifted during the takeoff roll, the rudder's deflection would have produced a strong yawing moment to the left, overpowering any corrective inputs and leading to the swerve and subsequent runway excursion.